Iron core pieces for use in a motor core are generally formed by a successively transferring die or mold, in which core pieces are punched out by means of a punch into a die. Therefore, burrs are produced along punched edges, and particularly burrs are generated along edges of slot holes. When a coil is wound into the slot holes, coil windings are liable to be injured by these burrs.
In order to avoid such disadvantage, in Japanese Patent Laid-open Publications 4-331444, 5-38106 and 6-141516, there have been proposed several methods for removing burrs. In a Japanese Patent Laid-open Publication 8-250320, there has been proposed a method for removing burrs, in which burrs are mutually pushed down by punching out iron core pieces in a direction opposite to a usual punching out direction. Furthermore, there has been proposed another method, in which burrs are removed by a barrel finishing after stacking a plurality of punched out iron core pieces.
In the above mentioned known methods, burrs are removed or pushed down such that coil windings are not injured by burrs. However, such methods require additional processes such as the barrel finishing and insulating treatment, and therefore the production of the laminated iron core is complicated and gives low cost performance.
Moreover, in the known methods, after removing burrs, an electrically insulating material serving as an adhesive agent has to be applied or coated on surfaces of the iron core pieces. This makes the methods much more complicated.
The present invention has for its object to provide a laminated iron core, in which the influence of burrs can be removed or mitigated without requiring a complicated addition process and a coil can be wound easily and safely.
It is another object of the present invention to provide a method and a progressive die machine for manufacturing such a laminated iron core.